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SPECIAL ISSUE 2008DYNAMIC VOLUME IMAGING

Dynamic volume images made with Toshiba's Aquilion ONE

One study with one injection for acute strokeAquilion ONE: the world’s first dynamic volume CT

Toshiba Medical System’s Aquilion ONE is a quantum leap in CT imaging that

can perform a multiphase study of the entire brain with only one injection of

contrast media.

The wide coverage provided by the Aquilion ONE’s 16cm detector, which has 320

detector rows, can scan the brain or heart in less than a second. So you can see an

entire organ in 3D with perfect continuity along the z-axis. Or see it in 4D, moving

as time passes. Or see it extremely fast, with a lower contrast medium dose and

exposure dose.

The Aquilion ONE will bring you dynamic views of the body you could not see

before. The next leap forward in CT technology that will revolutionize patient care.

Are you ready for your next step?

Toshiba: Made for Patients, Made for You, Made for Life!

www.toshiba-europe.com/medical

ULTRASOUND CT MRI X-RAY SERVICES

SPECIAL IMPRINT

Imprint

Publisher:TOSHIBA Medical Systems Europe B.V.,Zilverstraat 1, NL-2718 RP Zoetermeer

Tel.: +31 79 368 92 22Fax: +31 79 368 94 44

Email: [email protected]

Editor-in-chief: Jack Hoogendoorn

Editorial review:CT: Dr Jörg Blobel

MR: Faiza Admiraal-BehloulX-ray: Bob Eastick

Ultrasound: Dr Jörg Schlegel

Printing: VVA, Düsseldorf

Subscription Service:Tel.: +31 79 368 92 71


TOSHIBA Infoline:Austria: +43 2236 616 23

Germany: +49 2131 180 91 23Belgium: +32 3 3262 323

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United Kingdom: +44 1293 653700Russia: + 7 095 975 2497

Switzerland: +41 1 929 6666The Netherlands & other countries:

+31 79 368 99 99Head Office Europe: +31 79 368 92 22

© 2008 by TOSHIBA Medical Systems EuropeAll rights reserved

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Rotation

Phase

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The world has been waiting for this.

SPECIAL EDITORIAL

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Dear reader,

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The major advantage of computed tomography over other imaging modalities is the excellent spatial resolution of anatomical structures down to the sub-millimeter range.

The disadvantage of CT has been – to date – its limitation with regard to functional diagnostics. With its volume detector of 16 cm width, the Aquilion ONE overcomes this disadvantage. A new CT generation will visualize the functioning of entire organs, for example the heart or the brain, within lessthan half a second scan time and with a voxel resolutionsmaller than 0.5 mm. Aquilion ONE rings in the era of dynamic volume computed tomography.

Over the next few months,clinical research and industry will jointly developnew dynamic volume CT diagnostic strategies. The following articles provide a first impression of the methodological principles and initial clinicalexperiences.

The future of CT has justbegun!

PD Dr P RogallaDirector CT Division Charité Campus Mitte Berlin, Germany

Dr J BlobelChief Clinical Science

TOSHIBA Medical Systems Co. Tokyo, Japan

Charité, Berlin in November 2007:positioning, installation and initialoperation of the new Aquilion ONE

as well as the experience with the first patients has demonstrated

that the new dynamic volume CT scanner opens up new vistas indiagnostic computed tomography.

The results surpassed all expectations. Particularly in cardiac

imaging the radiation dose can be reduced significantly without

any loss in image quality.Page 15

The spatial image voxels and the data acquisition time are allelements of dynamic volume CT.

Even when looking at dose equivalency, high and low contrast

resolution of the Aquilion ONE, the first dynamic volume CT

scanner, compare favorably withthe results of the Aquilion 64.

Compared with the helical scan ofa 64 MSCT and its standard pitch

of 0.2 for cardiac scanning, thelack of oversampling in dynamic

volume CT reduces radiation exposure by 80%. Page 20

SPECIAL CONTENTS

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Editorial

R Irwan, H B K de Vries, L Bouwman, H ZomerThe History of Computed Tomography

Installation of Aquilion ONEInterview with Claude Moinier, Kees Kalkman and Koji Umehara of Toshiba Medical Systems

P Rogalla, J Mews, J Hall, H Meyer, P Hein, A LembckeDynamic volume CT imaging: workflow and initial experience

J Blobel, N Sugihara, J Hall, J Mews, H KuraImage quality basics of the dynamic volume CT Aquilion ONE

A Lembcke, P A Hein, J Mews, J Blobel, P RogallaCardiac Imaging with the 320 DetectorRow CT

R Irwan, H B K de Vries A brief summary of patient doses of dynamic volume CT

E SiebertInitial Experiences with the 320 DetectorRow CT in Neuroimaging

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15

20

24

28

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Special: Dynamic Volume Imaging

Computed Tomography

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I Parienty, F JouniauxFresh Blood Imaging and Time-SlipBreakthrough techniques for non-contrast MRA investigations of peripheral and renal arteries in patients with renal insufficiency

T YoshieARTIDA – Improving clinical performance with innovative technology

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44

MRI

Ultrasound

Artida’s basic philosophy centers onadvanced transducer design to provide better data, faster and moreflexible signal processing to extractmore information more quickly. The final result is improved clinicalperformance and a host of toolsthat provide new ways to assess 2Dand 4D ultrasound data. Page 44

A further, altogether new area ofapplication in non-invasive diagnos-tic cardiac imaging is myocardialperfusion imaging by computedtomography. In dynamic scanningmode the CT scanner is able torecord the volume data of the entireheart, either continuously during aspecific interval or intermittently incertain time intervals.Page 24

IntroductionComputed tomography (CT) scanners have un-

dergone continuous development and gained wide-spread acceptance as one of the most innovativemedical imaging modalities to date. The most sig-nificant application of CT lies in the diagnosis ofneurological, cardiological and oncological dis-orders.

The art of CT is constantly evolving and the lastyears have seen new systems with more and morerow detectors. These CTs are able to increase bothscanning speed and image quality compared tosingle-row systems.

The following brief history of CT technology,starting from the early days, focuses on the firstToshiba CT scanners and the development of the de-tector systems which to a great extent determineimage quality.

Discussion of clinical applications or fundamen-tal technical details is beyond the scope of thisoverview and can be found in a number of texts1-3

and the references therein.

The development of CTFor the first fifty years of radiology, the primary

examination involved creating an image by focusingX-rays through the body part of interest and direct-ly onto a single piece of film inside a special cassette.In the earliest days, a head X-ray could require up toeleven minutes of exposure time and the patientshad to hold the cassettes themselves. Today, X-rayimages are made in milliseconds and the X-ray dosecurrently used is as little as 2% of what was used forthat eleven minute head exam 100 years ago.

Early development of CTAllan Cormack and Godfrey Hounsfield investi-

gated independently how the limitations of X-rayscould be tackled to reconstruct an accurate cross-section of an irregularly shaped object. In 1979, bothCormack and Hounsfield received the Nobel Prize forphysiology and medicine for the development of CT4.

Seven years before being awarded the NobelPrize, Hounsfield had patented the first CT scanner.He is considered to be the father of CT since he de-veloped a method which is the foundation of today’sCT, the EMI (Electrical and Musical Industry) scan-ner. This prototype, originally intended for examina-tions of the head, took hours to scan the first patientand five minutes to acquire each image.

Development of Toshiba CTThe direct association of Toshiba with CT dates backto the installation of the first EMI head scanner inJapan in August of 1975 at Tokyo Women’s MedicalCollege6. Business collaboration between ToshibaMedical Systems and EMI Medical, the original

R IrwanH B K de Vries

L BouwmanH Zomer

The History of Computed Tomography

SPECIAL COMPUTED TOMOGRAPHY

4

Fig. 2: The second-generation CT scanner (TCT-35A) ,launched in 1977, was based on translation/rotationtechnology and had eight detectors.

Fig. 1a: Allan Cormack(with permission of theNobel Prize Foundation)

Fig. 1b: GodfreyHounsfield(with per-mission ofthe NobelPrize Foundation)

A year later, in 1978, Toshiba’s accumulation ofexpertise was demonstrated by the launch of awhole-body CT scanner, the TCT-20A (Fig. 5), whichmarked the beginning of successful clinical practice.The translation/rotation technology was replaced bya rotation/rotation configuration - the third genera-tion of CT scanners. This technology was developedto reduce scan times to approx. 1.8-6 seconds.

Furthermore, in this third generation Toshiba alsointroduced the worldwide first direct magnificationsystem to vary the distances between the X-raytube/patient and patient/detectors according to thesize of the part of the anatomy being scanned (Fig.6). The resulting image was much better than thatproduced by scanners of previous generations.

Helical scanningIn the early 1980s, Toshiba patented an innova-

tive scan technology called helical (or spiral) scan-ning where true con-tinuous scanning hasat last been achieved7.This remarkable inno-vation made availablea number of clinicalapplications that had

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Fig. 5: Toshiba’s third-generation CT scanner (TCT-20A) based on rotation/rotation technologywith 1.8-6 secondsscan time

Fig. 4: One of the first Toshiba CT consoles

Fig. 3: First brain CT images of 160 x 160 matrix (left) and 240 x 240 (right) whichtook 45 -130 seconds to reconstruct. They were both of 5 mm slice width.

inventors of CT, continued but soonToshiba began to manufacture its ownbrain and whole-body scanners. The de-velopment of Toshiba CT scanners can becategorized into three main phases:1. axial scanning2. helical scanning3. volume scanning.

Axial scanningAxial (often called “step-and-shoot”) scanning

characterizes the first Toshiba CT generations inwhich a slice was acquired from a fixed tube position.

While the single detector CT scanner with trans-lation/rotation geometry represents the first-gener-ation CT, the second-generation CT scanner had eightdetectors with the same geometry as the first gener-ation. This translation/rotation geometry will be ex-plained in more detail below.

Figure 2 shows a Toshiba second-generation CTscanner, the TCT-35A, launched in 1977. It could pro-duce a matrix of 160 x 160 or optionally 240 x 240(Fig. 3 left and right, respectively). The physicianswere fascinated by the ability to see the soft tissuestructures of the brain including the black ventricles.

Figure 4 shows one of the first CT consoles whichpioneered image reconstruction and offered the firstremote control between a Toshiba CT scanner and thecomputer server.

been inaccessible to conventional axial CT scanners.Helical scanning technology is the basis of mostcommercially available CT scanners today.

During a helical scan, the table moves at a con-stant speed as the X-ray tube performs a continuousrotating scan as demonstrated in Figure 7.

The large volume of data gathered enables a largearea of the body to be examined during a singlebreath-hold. This produces sharper images, includ-ing 3D and MPR, as well as improved diagnostic ac-curacy.

A slip-ring is employed to transmit power bet-ween the gantry and the rotating X-ray high-volt-age generator assembly. Figure 8 shows early high-voltage tests of a slip-ring gantry at Toshiba MedicalSystems Center. Rotational tests were successful atspeeds of up to two revolutions per second.

Fourth-generation CT was characterized by a design using a stationary detector ring and rotatingX-ray tube. The TCT-900S/x (Fig. 9) was the firstfourth-generation Toshiba helical scanner being ableto combine high-speed scanning with rapid backand forth table top movement.

In addition, not only interscan delays are elimi-nated by using nutate/rotate geometry but also aspatial resolution of 0.35 mm has been achieved.

Nutation is a slight irregular motion in theaxis of rotation of an object as the X-raytube is positioned outside the dectector ring(Fig. 10). This nutation/rotation configura-tion reduces the number of detectors and theradius of the detector ring. Furthermore,since the effect of focus size on spatial reso-lution is minimized, a large focal spot can beused to deliver a high X-ray dose, yieldinghigh-quality images.

Dynamic volume CTAlthough helical scanning was an innovative

breakthrough in CT scanning, Toshiba continues tobe the leading innovator in CT technology by devel-oping the dynamic volume CT scanner (Fig. 11). Anissue of helical scanning was that the patient tablemust be moved to scan the entire heart, which


6

Fig. 7: The basic principle of helical scanning meant a quantum leap in the advance of CT technologypatented by Mori6 in theearly 1980s.

Fig. 6: Another third-generation Toshiba

whole-body CT scanner (TCT 60A)launched in 1978

which incorporated the principle of geo-

metric magnificationby changing the

source/patient and patient/detector

distance.

requires additional time. This may lead to a mis-match of temporal phases between the upper andlower ends of the scan range.

Dynamic volume CT permits the entire heart to beexamined without the need for the helical scan. Inother words, the entire heart can be captured in asingle rotation for coronary analysis, or over a singleheartbeat to include complete functional diagnosis.Moreover, volume scanning allows acquisition ofmultiple low-dose volume scans of the entire brainduring contrast infusion to provide whole brain per-fusion and whole brain dynamic vasculair analysis inone examination.

DetectorsEarly development

The detector is one of the most important partsin a CT system as it determines image resolution andacquisition speed. The X-ray tube and the detectorare positioned opposite to each other. In the first-and second-generation CT scanners (see also Fig. 5),the detectors and the X-ray tube move through a se-ries of linear translates and rotates around the pa-tient’s head as demonstrated in Fig. 12. A number ofdetectors is situated directly opposite the X-raytube. The detectors and the X-ray tube move througha series of 30 linear traverses by 6º between eachtraverse until the full 180º rotation is complete.

The detector acquires the attenuated X-rays andconverts them to visible light, which in turn is con-verted into digital signals by high-speed electronics.Powerful computer create high-resolution CT imagesin real-time.

Development of Toshiba detectors for multislice CT

From the commercial point of view, as the num-ber of rows increases, development work becomesboth more difficult and more expensive. However,the increase in the number of rows was unavoidabledue to the following needs8:• higher spatial resolution• higher time resolution (speed to convert X-rays to

electronic signals)• better low contrast resolution• lower exposure dose.

Toshiba has been able to achieve the minimumslice thickness of the detector of 0.5 mm which de-termines the resolution in the longitudinal direction.Transmitted X-rays are detected and converted intoelectrical signals by the selectable slice-thicknessmulti-row detector (SSMD).

7Fig. 10: Nutation/rotation configuration. The X-raytube (yellow) is placed outside the detector ring.

Fig. 8: High voltage tests on the first slip-ringtechnology. Speeds up to two revolutions persecond were achieved6.

Fig. 9: A fourth-generation CT helical scanner (TCT-900S/x) which eliminates interscan delays

by the use of nutate/rotate geometry and slip-ring technology

The 4-slice SSMD had some advantages over thesingle-slice detector in terms of reduced penumbra(Fig. 13) and therefore exposure dose. However, theunused penumbra continued to be an issue as thepatient was still exposed to unnecessary X-rays.

Therefore, 8-slice and 16-slice SSMD systemswere introduced to reduce X-ray radiation further byapproximately 20% and 40%, respectively3. The keyfor exposure reduction in the development of X-rayCT systems is to improve detec-tor efficiency. All manufacturershave therefore been striving todevelop new materials for scin-tillators. Toshiba is also explor-ing new materials for its next-generation detectors to improveefficiency by approximately40% compared to conventionalscintillators. The efficiency ofToshiba's current detector sur-passes that of competitors. In-efficient scintillators lead to adeterioration of image qualityeach time the number of detec-tor rows is increased and slicethickness is reduced.

In clinical applications, thestent lumen was virtually invis-ible in a 8-slice system. Im-proved visualization using 16-slice system was reported, inparticular in stents with either alarge diameter or thinnerstruts9,10.

In 2003, the first 32-sliceSSMD system (Aquilion 32) wasintroduced which strived for

further reductions in X-ray exposure and further im-provements in patient- and user-friendliness in CTexaminations. Like the Aquilion 16, this system is amultislice helical CT that supports whole-bodyscanning.

One year later, the first 64-slice SSMD system(Aquilion 64) was launched. With a 64-slice systemthe entire heart can be covered in a few heartbeatswhich increased temporal resolution and lowered

the dose compared to previoussystems.

320-slice detectorFor volume scanning, 320

detector rings (Fig.14) were in-troduced which produce iso-tropic resolution of 0.35 mmvoxels. The major benefit of320-slice CT is the increasedspeed of volume coverage.

This latest technology hasdemonstrated the potential tosignificantly reduce radiationexposure by eliminating the


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Fig. 12: Detectors are positioned opposite to the X-ray tube. The early technology where the tube and detectors move in a linearfashion across the patient (top) and rotate around the patient (bottom) by each traverse (see also Fig. 5).

Fig. 11: The volume scan-ner Aquilion ONE,which was intro-duced at RSNA2007, is able toscan the entire heart or head witha single rotation.

requirement for a helical examina-tion in both cardiac CT angiogra-phy (see related article in this is-sue) and whole-brain perfusionstudies for the evaluation of stroke.

This allows large volumes (up to16 cm coverage) to be scannedwithin one single rotation follow-ing intravenous administration ofcontrast agent; this has particular-ly benefitted CT angiography tech-niques - which rely heavily on pre-cise timing to ensure gooddemonstration of arteries.

Last but not least, Toshiba hasdeveloped and released image re-construction techniques (MUSCOT,TCOT and ConeXact) optimized foreach CT generation - from 4- to16- and 64-row CTs as well as the320-row CT. We are pleased to saythat the image quality of our CT isconsidered the best in global mar-kets such as Japan, USA and Eu-rope. For the past ten years, an im-age quality issue for CT has been tominimize the cone angle effect as-sociated with the increase in the number of detec-tor rows. We are therefore proud that the release ofthe world's first dynamic volume CT Aquilion ONETM

has proven our image reconstruction technique isthe world's most advanced technology.

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AcknowledgmentWe thank Hans Baartman for his valuable comments.

Toshiba Medical Systems Europe BV,Zilverstraat 1 2718 RP ZoetermeerThe Netherlands

Fig. 13: Penumbra has been an ongoing issue in the development of multislice CT

SummaryWe hope we have giv-

en you a brief overview ofthe history of CT in termsof the fundamental re-search, evolution and lat-est development, al-though it is impossible tocover all aspects in detail.In short, CT continues tothrive on innovation andto broaden its scope, ap-parently without limit.The heart and brain ofcomputed tomography,however, remains thework by the scientistsmentioned above.

References1 S. Saini, GD Rubin, MK Kalra (eds.), “MDCT, a practical approach”,

Springer, ISBN 88-470-0412-5.2 MS Budoff, S Achenbach, J Narula (eds.), “Atlas of Cardiovascular CT”,

Springer, ISBN 978-1-57340-267-53 I Mori, T Suzuki, “Development of Advanced Multislice CT scanner

Aquilion”, eMedical Review.4 http://nobelprize.org/nobel_prizes/medicine/laureates/1979/5 GN Hounsfield, “Penetrating radiation examining apparatus having

a scanning collimator”, U.S. Patent No. 3,866,047, filed in 1973, is-sued in 1975.

6 I Mori, “Computerized Tomographic Apparatus Utilizing a RadiationSource. U.S. Patent No. 4,630,202, filed in 1983, issued in 1986.

7 S Makino, JF More, K Saito, CR Smith, “Development of an AdvancedCT scanner”, Medical Review No. 19, 1988.

8 M Okumura, M Tamatani, K Igarashi, “Development of x-ray detec-tor for multislice CT with 0.5 mm slice thickness and 0.5 second rev-olution”, Proc. SPIE 4682, 2002.

9 JD Schuif, JJ Bax, JW Jukema et al, “Feasibility of assesment of coro-nary stent patency using 16-slice CT”, Am J Cardiology, 94:427-30,2004.

10 F Cadermartiri, JD Schuijf, NR Mollet, P Malagutti, G Runza, JJ Bax,PJ de Feyter, “Multislice CT coronary angiography: how to do it andwhat is the current clinical performance?”, European J of Nuc Medand Mol Imaging, 32(11), 2005.

Fig. 14: Recently introduced 320 detectorrings (0.5 mm) cover a 16 cm object range and are able to scan the whole heart in one rotation.

Installation of Aquilion ONE™


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The Aquilion ONE dynamic volume CT, from Toshiba Medical Systems, has most recently beeninstalled in two leading academic hospitals in Europe. With systems already in use in Japan, theUSA and Canada and further orders received from all over the world, the Aquilion ONE is alreadystarting to create new global standards in imaging diagnostics. Leiden University Medical Centre(LUMC) in Leiden, the Netherlands, and the Charité University Hospital in Berlin, Germany, werethe first in Europe to acquire this new technology.During the installation of the Aquilion ONE in Leiden, VISIONS talked to Claude Moinier, ServiceSupport Manager, Kees Kalkman, Senior Product Specialist of the Technical Support Group fromToshiba Medical Systems Europe and Koji Umehara, Deputy Manager CT Systems Division fromToshiba Medical Systems Corporation in Japan. They explained to VISIONS what was involved ininstalling the Aquilion ONE.

Claude Moinier, Koji Umehara, Kees Kalkman

(from left to right)

First installation of the Aquilion ONE in the Leiden University Medical Centre

VISIONS: LUMC is one of the first European hospitals to acquire the Aquilion ONE. What hasprompted the decision to install the system?

Claude Moinier: Providing outstanding regional,national and international medical services and re-search, LUMC is affiliated to Leiden University in TheNetherlands. It has 867 beds, approximately 7000staff and clinical departments in all medicalspecialities. The hospital acts as a tertiary referralcentre for the northern part of the province of SouthHolland, as well as coordinating a wide range of re-search programmes in both clinical and basic med-ical research. LUMC holds an internationally recog-nised position as a centre of excellence in research.Its special units include neurosurgery, cardiothoracicsurgery, neonatal and paediatric surgery and inten-sive care, paediatric oncology and a level I traumacentre. The wide area detector of the Aquilion ONE,being 16 cm, covering entire organs in just one ro-tation, allows clinicians to visualize flow and dy-namic motion, giving not only morphological butfunctional information. Faster and more precise di-agnostics for a wide range of applications are nowin reach of clinicians and patients.

Kees Kalkman: LUMC and Toshiba MedicalSystems have a long-standing relationship overmany years. Having started with nuclear medicine,back in the 70s, this cooperation was extended sev-eral year ago to CT (computed tomography). The new Aquilion ONE CT system, which is being installed atthe hospital, complements a 64-slice and a 16-sliceCT, both of which are Toshiba scanners.

Koji Umehara: The hospital takes pride in pro-viding the best possible quality regarding both med-ical technology and patient care. It committedeagerly to the state-of-the art Aquilion ONE CT, to-wards making further improvement to the hospital’s(already excellent) record in quality and time of di-agnosis, and to effect a further reduction in costs.LUMC was highly impressed by the system’s ad-vanced capabilities and fully confident in Toshiba’sconsistent support services.

VISIONS: Are there any special considerations that need to be made before installation of the Aquilion ONE can begin?

Kees Kalkman: Toshiba’s installation team en-sured that LUMC was well prepared to receive thenew system. It goes without saying that this newtechnology requires specially trained engineers forinstallation and what’s more important, to assurehigh-quality service. Therefore, we received exten-sive training in Japan. Also Japan supported the firstEuropean installation by sending their most skilledengineers, all to ensure that the new Aquilion ONEwill run smoothly from day 1 onwards.

VISIONS: How was the system transported to its operational site?

Kees Kalkman: The Aquilion ONE was manoeu-vred through the LUMC building and into the CTroom with the aid of a crane. To facilitate transportand lifting, the Aquilion ONE has been designed withspecial winching hooks.

VISIONS: The Aquilion ONE is more powerful than the present generation of CT scanners, is it also much bigger?

Kees Kalkman: The system itself is very muchcomparable to our Aquilion 64 and Aquilion 16.However, due to a larger scannable range the Aquilion ONE requires a slightly larger working space.

Accurate testing of all CT scanner parameters isa crucial part of a good quality control programme.This is done using phantoms – these are cylindrical,water-filled structures used for calibrating CT (andMRI) systems to ensure the quality of images.

VISIONS: What about the power requirements of the Aquilion ONE?

Koji Umehara: Aquilion ONE is a significantlymore powerful machine than presently available CTscanners. Both in diagnostic performance as well asin processing the big amount of clinical images. It

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goes without saying that adequate capacity fordealing with the heat, generated by the powerful re-construction units must be taken into consideration.The existing power supply and cooling capacity ofthe CT room at Leiden was examined when planningthe machine installation and proved to be sufficientfor the system.

The Aquilion ONE has been designed to be as en-ergy efficient as possible. It reuses the kinetic ener-gy produced in the breaking of rotations to reducetotal energy consumption. This is known as an ‘ecodrive’ function and can help reduce the overallenergy requirements.

VISIONS: With these distinctive product features in mind, is the technical installation of the system also different?

Koji Umehara: The installation time of the newAquilion ONE has proved to be very similar to thatfor the Aquilion 64. A great deal of effort has beenmade to ensure that the Aquilion ONE is as easy andefficient to install as other Toshiba machines.

Claude Moinier: This is largely due to the factthat the installation design has deliberately beenkept as close to the Aquilion 64 as possible. ToshibaMedical Systems not only considers the needs ofend users of its systems in all stages of product de-velopment – the hospital’s clinicians, techniciansand patients - but also of the Toshiba service engi-neer as an integral part of the process. The fasterand easier the system can be installed, the less in-vestment is required by the customer. In addition,any margin for error is absolutely minimized.

What’s more the close resemblance in user inter-face not only facilitates interventions by servicestaff, but also assures that Toshiba customers canlearn the scanning procedures on the Aquilion ONEin a considerable shorter period.

Koji Umehara: The installation has been kept assimple as possible through the use of well-labelledconnections and one-fit-only connections. From thedrawing board through every stage of development,Toshiba has considered the needs of the service engi-neer and, in-turn, optimized efficiency of installation.

VISIONS: Are there any operational considerationswith the Aquilion ONE which Toshiba’s installationteam helps prepare its customers for?

Claude Moinier: There are a small number of op-erational differences with the Aquilion ONE whichcustomers need to consider before installation iscomplete. Toshiba’s installation team provides ex-pert advice to ensure that every aspect of operationhas been considered in setting up the system and in-tegrating it seamlessly into daily use.

Kees Kalkman: Visualization of dynamic process-es over a wide area, without the need to move thepatient, will generate a large amount of clinical im-ages which need to be reconstructed and visualizedat high speeds. Toshiba has incorporated many moreoptical connections inside the machine to enable itto deliver data faster and with greater volume.

VISIONS:Does the more complex internal architecture of the Aquilion ONE mean it is moredifficult to integrate, operate and interact with?

SPECIAL

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COMPUTED TOMOGRAPHY

The first test runof the Aquilion ONE

Claude Moinier: Absolutely not! The new Aquilion ONE is entirely geared towards PC compat-ibility, giving even more flexibility than previoussystems. As mentioned earlier the operator interfaceis very very similar to the Aquilion 64.The image quality handling procedurefor calibration and maintenance fol-lows that of the Aquilion 64, too.

VISIONS: Once the system is installed, is maintenance the same as the Aquilion 64?

Claude Moinier: Some aspects arethe same; most notably that Toshibacontinues to provide a comprehensivetechnical support system, as it hasdone effectively at LUMC for manyyears. Toshiba’s service team can helpwith solving any problems via remoteaccess – as with the majority of ourlater CT systems. InnerVision is our re-mote diagnostic service which pro-vides proactive support and quality as-surance. The system periodicallymonitors our imaging equipment toensure it is always delivering the clin-ical excellence required.

If a problem is detected, highly trained servicestaff of our “StandbYou” service are available to car-ry out online diagnostics to identify and resolve theissue. Experts are able to explore online solutions

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Step by step: installing the new CT atthe UniversityHospital Charitéin Berlin, Germany.

and frequently resolve them without the need for anon-site service.

Preventive measures mean less unscheduleddowntime for the hospital. Automated predictive di-agnostics alert Toshiba to a potential issue before itbecomes a problem. Proactive monitoring helps min-imize costly downtime and the need to rescheduleexaminations and helps in the long-term improve-ment of quality standards in our products.

Kees Kalkman: Toshiba offers various levels ofmaintenance for more security and insurance appro-priate for the advanced science of the Aquilion ONE.

VISIONS: Aside from effective installation andmaintenance is there anything else which can ensure the longevity of the Aquilion ONE?

Koji Umehara: Toshiba thinks ahead to the nextfive to ten years in product design and invests onlyin technology that has long-term prospects. This en-sures that all our systems deliver optimal perfor-mance for the maximum time from installation toeventual replacement. The Aquilion ONE has beendesigned to be relatively easily upgradeable. All oursystems are also developed with the same principlein mind.

VISIONS: So installation of the Aquilion ONE is not just a distinct technical procedure for Toshiba,but part of a continuum of interactive and integrated service and development?

Koji Umehara: My focus is on the CT business, in-cluding CT design interface with service, marketingand quality. An important part of my role is to relayour Aquilion ONE installation experiences at LUMC toToshiba Medical Systems global headquarters inJapan. Installation issues are a critical part of pro-duct and service design and through this, and manyother channels, our expertise can be honed furtherinto the future.

Claude Moinier: At Toshiba, a CT installation isnot carried out by an isolated team. The EuropeanService Group delivers training, education, serviceplans and if necessary troubleshooting. In this way,installation becomes an integrated aspect of service,which optimizes every aspect of delivery to our cus-tomers. The teams operate all over Europe and alsowork on all modalities.

Kees Kalkman: Despite the fact that the Aquilion ONE is such an advanced product, its in-stallation and operation are virtually identical to a64-slice CT scanner. The role of every person whocontributes to the installation, operation and enduse of the machine has been well considered in de-sign and development not just of the product itself,but also of the supporting services.

VISIONS: Thank you!


14

After the storm: the engineers proudly present theirmasterpiece at the Leiden University Medical Centre(LUMC), The Netherlands.

15

Fig. 1: Lowering the new Aquilion ONE intothe examination room(courtesy of L. Krug)

The waiting is over: on 9 November 2007, thenew dynamic volume CT scanner Aquilion ONEwent into operation at the Charité UniversityMedical Center in Berlin, Germany. A heavy-dutymobile crane had to lift the gantry and slowly moveit through the window of the new examinationroom (Fig. 1). Installation, adjustment, calibrationand start-up of the system were completed withinjust seven days. Approval by the local regulatoryauthorities went smoothly despite the fact that thestandard testing procedures for dosimetry had to beadapted to the new technology of the dynamic volume CT unit. It was quickly established, though,that all technical specifications were adhered toand that both low- and high-contrast resolutionsnot only corresponded with those of the 64-slice CTproducts but even surpassed them in some areas.

The first patient studied after the unit went intooperation presented with non-specific thoracic painand a CT scan was performed in order to rule out

coronary heart disease. Having been on long-termoral medication with beta-blockers she exhibited aresting pulse rate of 76 beats per minute (bpm).With the new CT scanner we were able to study hercoronaries without the need for any intravenous (i.v.)medication. Even without previous training on thenew system we were able to generate high-qualitydiagnostic images – due also to the new user inter-face of the Aquilion ONE. Since it relies on the samefunctional logic as the previous models, apart fromthe technical data of the new CT technology, com-prehensive training was not considered mandatory.

Study modesCurrently, apart from a 64-slice spiral mode the

system offers three different examination modes forcomputed tomography: • stitching mode (for whole-body scanning)• dynamic scanning mode (for dynamic studies and

perfusion imaging)

P Rogalla1, J Mews2, J Hall2, H Meyer2, P Hein1, A Lembcke1

Dynamic volume CT imaging: workflow and initial experience

SPECIALCOMPUTED TOMOGRAPHY

1Institute of RadiologyUniversity Medicine Berlin,Charitéplatz 1 10117 Berlin, Germany2CT Systems Division Toshiba Medical SystemsEurope BV, Zoetermeer2718 RP, The Netherlands

• ECG gating (when synchronization with the car-diac action is needed).

Stitching mode In this mode the CT scanner acquires sequential

images based on variable usage of the detector andjoins them automatically to provide complete imag-ing of the whole body. The distance studied is onlylimited by the maximum length of the examinationrange (current table length: 2.00 m). Only the veryexperienced eye will notice that the resulting im-ages were not acquired in a helical scan. Since thetime interval between each acquisition is just 1.7 sincomplete breath-holding will only result in minoranatomical changes. Particularly when dealing withcritical injection protocols, initial experience hasdemonstrated that in low volumes differences invascular contrast may become visible if high flowrates are employed. But it should be noted thatthese differences in perfusion are also seen in heli-

cal CT studies, although not as clearly since the dif-ferences in density are blurred continuously over alarger area and do not show abruptly at an interface(Fig. 2). The initial concern that shifting from oneposition of the table to the next with its concomi-tant acceleration and deceleration might lead toproblems for the patient has turned out to be un-founded. The table accelerates and decelerates sosmoothly that to date there have been no com-plaints even by patients sensitive to motion.

With the new CT scanner planning of the area tobe studied is done in the same fashion as with theAquilion 4- to 64-slice CT models. Once the area tobe examined has been defined the optimum subdi-vision into individual images by variable usage ofthe detector is computed on the console. Thisensures that the examination area selected willneither be too large nor too small. The individual

images are joined fully automatically – a processwhich requires no intervention by the radiologist.Thin as well as thick layers and multiplanar recon-structions can be generated in the same automaticfashion. Moreover, various reconstruction kernels aswell as different destinations for the images can beselected (Fig. 3: Screenshot of the user interface).

Dynamic imagingThis mode of operation is designed for imaging

time flow in computed tomography, for examplejoint movement, perfusion imaging or ventilation ofthe lungs. Temporal resolution is defined by the se-quence of individual images and continuous as wellas intermittent acquisition with arbitrary intervalsand combinations of these acquisition modes arepossible (Fig. 4: Protocol for pancreatic perfusion).Thus, the protocol for a perfusion study of the headmay differ from the acquisition protocol of a dy-namic series of the pancreas. Typically, abdominal

applications require fast data acquisition at the be-ginning of the arterial perfusion phase, whereas lat-er on in the sequence larger intervals between theacquisitions are acceptable. Image reconstructioncan be influenced by priorisation, i.e. later imagesin the sequence can be viewed first. All images canbe sent from the console as a dynamic volume in thenew Enhanced DICOM format and are available al-most immediately for post-processing.

In order to keep the dose profile in perfusionstudies within the normal range of diagnostic CT,each image is generated in low-dose mode; usual-ly, we work with about 80 kV and 50 mAs, result-ing in an effective radiation exposure of 0.6 mSvper scan. This allows for imaging of 10-20 se-quences without increasing total exposure signifi-cantly beyond the scope of a diagnostic CT scan ofthe same region.


16

Fig. 2: Example of a thoracic CT study in

stitching mode. The finalimage has been conjoinedseamlessly from the three

individual images.

Fig. 3: Screenshot of theuser interface during planning of a whole-body scan. Employing a variable proportion of the width of the detector ensures precisedelineation of the area to be examined.

Fig. 4 a: Screenshot of the time sequence; perfusion image protocolwith 80 kV and 50 mAsper volumetric scan

ECG gatingThis mode of operation is used primarily in car-

diac imaging applications. Three basic imagingtechniques are possible, with prospective scanningbeing realized by defining a study time frame with-in the RR interval. This very effectively reduces ra-diation exposure. While prospective data acquisi-tion from two heart beats may shorten the effectiveexposure time, radiation exposure will increase witheach image. Continuous acquisition of an entireheartbeat offers the option to reconstruct completevolume data sets retrospectively for any point intime within the RR interval. However, in this caseradiation exposure will not be significantly less thanwith a state-of-the-art 64-slice CT scanner (Fig. 5).

17

The key breakthrough in cardiac imaging is theincreased detector length: 16 cm. Such a detectorallows to study the entire heart without having toreposition the table. Overlapping scanning mode asrequired in 64-slice CTs is no longer necessary. Thecomparatively high radiation exposure in CT of theheart is almost entirely due to overlapping scan-ning in helical mode. This so-called overscanning(low-pitch scanning) is needed to ensure that eachlocation will be imaged at each point in timethroughout the RR interval. The fact that the Aquilion ONE does not require helical scanning ofthe heart reduces radiation exposure down to onequarter or one fifth of a comparable study with a64-slice CT scanner.

Apart from this dramatic reduction in dose, thereis another important aspect: with the first 100 pa-tients we quickly noticed that cardiac arrhythmia –be it absolute arrhythmia or heart rates up to 130bpm – does not constitute a contraindication forcomputed tomography of the heart! Online assess-ment of the imaged RR interval by the software ofthe new CT unit ensures that image reconstructioncan proceed as planned. If the patient experiencedan unexpected extrasystole or if there is insufficientdata of one image for artefact-free reconstruction,the scanner will automatically image one addition-al heartbeat in the same fashion and without any

noticeable time-delay. The user can set beforehandthe maximum number of heartbeats to be consid-ered in image reconstruction, thus extrasystoleshave no impact on image quality. Due to the physicsinvolved, helical acquisition cannot offer a similartechnique. This is most likely the second dramaticbenefit of the new CT modality compared with stan-dard 64-slice computed tomography.

Initial experience with the new system has indi-cated that now radiation exposure in cardiac imag-ing is primarily dependent on the temporal resolu-tion to be achieved and therefore on the heart rateof the patient. The shorter the exposure time, thehigher the number of segments – and thus heart-beats - to be imaged, which in turn results in a lin-ear increase in radiation exposure. In this contextreducing the heart rate does not improve imagequality as much as it reduces radiation exposure.Heart rates below 65 bpm do not have to be reducedby beta-blockers, and the radiation exposure ofsuch cardiac studies is about one fifth the dose witha 64-slice CT scanner.

Clinical experience A surprising aspect of the new CT scanner is the

quiet running of the gantry. The CT scanner revolveswith hardly any vibration, and the oscillations in thehousing often present in older models are hardlynoticeable at all. Another improvement is the largeLCD monitor built into the gantry. On this screen,the patient can view not only his/her name (ensur-ing correct identification) but it is also possible todisplay the ECG or image sequences, e.g. in pediatricstudies. Furthermore, the table length of 2.00 m is


18

Fig. 5: Schematicdrawing of the

three acquisitionmodes in ECG gated

scanning

Fig. 4 b: Color depiction of a pancreatic metastasis in renal cancer. The colors reflect trueperfusion information.

Fig. 6: Cardiac CTdemonstrating a soft plaque in the leftmain coronary artery.With prospective ECG gating, the complete volumetricdataset was acquiredduring a single heartbeat.

helpful and advantageous not only in Accident &Emergency but particularly so in standard studies.The patient may be positioned in a more flexiblefashion and, if needed, the examination can be ex-tended without problem, for example when un-planned studies of the head and neck become nec-essary in abdominal and pelvic CT studies. Inaddition, in all examination techniques of the newCT scanner the gantry can be angled which is par-ticularly beneficial in studies of the head: the gantrycan be angled that the lenses of the eyes will remainoutside the examination area.

We had to get used to the time delay in imagereconstruction since, unlike in 16- to 64-sliceAquilion scanners, rapid reconstruction during im-age acquisition is not possible. The slight delay of afew seconds between image taking and viewing ofthe reconstructed images, however, impededneither the clinical workflow nor prompt imageassessment.

Simultaneous availability of the reconstructedimages on a second console by so-called data basesharing permits assessment right after image re-construction. The new 4D viewing mode is anotherexceptional benefit. Perfusion studies can be con-verted into a dynamic series rapidly and efficientlyon the monitor and may be viewed in flexible andinteractive fashion. After having checked imagequality and finalizing the study, the user decideswhether the image data will be sent in standard DICOM or the new Enhanced DICOM format. Anyadditional DICOM node and any compatible archivecan be addressed irrespective of the destinationslisted in the study protocol. However, smooth work-ing requires a 1 Gbit/s data link.

Conclusion Positioning, installation and initial operation of

the new Aquilion ONE as well as the initial experi-ence with the first 180 patients has demonstratedthat the new dynamic volume CT scanner opens up

new vistas in diagnostic computed tomography.Without extensive training on the new system wewere immediately able to take advantage of the newtechniques for our patients. The initial results sur-passed all expectations. Particularly in cardiac imag-ing the radiation dose can be reduced significantlywithout any loss in image quality. On the contrary:preliminary comparisons of patients with previousimages obtained by 64-slice CTs seem to indicate aslight advantage for the new CT system in terms ofimage detail and image definition. It is not yetknown if perfusion imaging – apart from studies ofthe head - will be of any clinical significance. Theinitial results are promising but extensive studies areneeded in order to demonstrate any diagnostic ad-vantage. A positive development is the fact that withthe new CT scanner perfusion studies can beperformed without any dose increase compared tostandard helical scanning. This should facilitate per-fusion imaging applications significantly. It shouldalso be emphasized that with the new dynamicvolume CT there are no limitations to whole-bodyscanning. Any organ region can be imaged in theusual quality, and the length of the examinationarea is determined only by the length of the table.

The new CT scanner proves once again that anynew technology can only be applied in meaningfulfashion if it is embedded in adequate infrastructure.For instance, if the infrastructure of the network isoutmoded, the image data cannot be efficientlytransferred to the consoles. Once again CT technol-ogy has leap-frogged ahead of the IT technologycommon to this sector. This innovation upsurge be-comes even more pronounced if one looks at thenew Enhanced DICOM standard: Apart from theVitrea Workstation (by Vital Images) today hardlyany workstation is able to employ this new com-munications protocol with its benefits of increasedtransfer rate and transmission of auxiliary data.Here, too, the new CT scanner will set the pace oftechnological progress in workstations.

19

IntroductionIn any imaging modality dynamic studies require

the interactive acquisition of spatial and temporaldata. In the past, the limited axial scan coverage of20 mm, 32 mm or 40 mm restricted assessment offunctional processes. The Aquilion ONE™ is the firstCT which can scan the complete volume of an organwithin a fraction of a second. With its axial scan cov-erage of 16 cm at the iso-center of the gantry thebrain, heart, pancreas and other organs can now bestudied dynamically. This paper discusses the variousparameters which impact on the spatial and tempo-ral resolution in dynamic volume computed tomo-graphy.

Spatial resolutionCT detectors with optimum spatial resolution re-

quire the smallest detector size possible and match-ing high signal sensitivity. The 320 detector rows,each with 896 detectors, generate a matrix of286,720 elements with a projected resolution of 0.5 mm x 0.5 mm at the iso-center of the AquilionONE. Compared with the 3° cone angle of the Aquilion™ 64, the wider 15° cone angle of the Aquilion ONE requires a new reconstruction algo-rithm. The new reconstruction algorithm ConeXact™was developed to overcome cone beam artefacts.

High and low contrast resolution were tested atCharité Berlin (Germany) on the Aquilion ONEinstalled in October 2007 and compared with theresults obtained with the Aquilion 64 in the samehospital. Figure 1 illustrates the phantom test com-parison in the axial view. With its phantom diameterof 15 cm the Bead Geometry Module CTP591 (ThePhantom Laboratory Inc., USA) comprises a diagonalarray of 0.18 mm and 0.28 mm pearls (Figure 1a).Since both types of CT scanner have an identicalgeometry of 0.5 mm detector elements, in axial MIPreconstructions (Figure 1b and 1c) the pearls are vi-sualized in the same homogeneous fashion. Theirdifference in size is also demonstrated quite clearly.For the test in Figure 1d the phantom underwent anadditional axial offset of 4 cm from the central planeand the gantry was tilted additional 15°. Comparedwith Figure 1c there was no difference in qualitywith the isotropic voxels used in image recon-struction. The sagittal views of both CT scanners(Figure 1 e-g) also did not yield any difference in ob-ject reproduction. With its reconstruction interval of< 0.5 mm and interpolation between the slices whenreconstructing with ConeXact, the Aquilion ONE willalso deliver a spatial resolution of < 0.5 mm in thesagittal plane comparable with that of the Aquilion 64. The adequate axial and sagittal images

J Blobel1, N Sugihara1, J Hall1, J Mews2, H Kura1

Image quality basics of the dynamic volume CTAquilion ONE


20

Fig. 1: Phantom test with a) rows of 0.18 mm and 0.28 mm

pearls (Aquilion ONE). Axial MIP reconstructions with b) Aquilion 64, c) Aquilion ONE,

d) Aquilion ONE, 4 cm off-center position, 15° gantry tilt.

Sagittal MIP reconstructions with e) Aquilion 64, f) Aquilion ONE, g) Aquilion ONE with 4 cm off-center position, 15° gantry tilt

(Test protocol: 120 kV, 25 mAs, FC 30, MIP)

ba

e

of the pearls (Figure 1b-g) demonstrate that in slicereconstruction the ConeXact reconstruction algo-rithm will maintain spatial resolution even for thegantry tilt. The axial scan field collimation was ad-justed with 4 cm for Aquilion ONE and 3.2 cm forAquilion 64 because of the 4 cm phantom width.

High contrast resolution after the ConeXactreconstruction primarily depends on detector geo-metry and only to a very small extent on the voxeldistance from the central axis in a slice image andthe distance of the slice images from the centralplane respectively. Since the images of the pearls areequivalent in all axial and sagittal MIP images ofFigure 1, this confirms voxel isotropy over the entirescan volume. The clinical example illustrated by theabdominal angiography in Figure 2 shows the highgeometric resolution of the contrasted vessels, basedon a voxel dimension of < 0.5 mm.

Low contrast resolution was tested with the 2.5 cm wide low contrast module CTP263 (The Phan-tom Laboratory Inc., USA) combined with the 14.5 cm total wide Catphan® Phantom 412 (16 cmdiameter). The axial scan field collimation was ad-justed with 14 cm for Aquilion ONE and 3.2 cm forAquilion 64. The same image reconstruction para-meters and low dose protocol with 120 kV and 100 mAs was employed for both CTs. The discern-ability of circular disks with a diameter of 2-15 mmand at various contrast levels from 0.1% to 1% wascomparable in the Aquilion 64 (Figure 3a) and theAquilion ONE (Figure 3b). This result is yet anotherindicator that the scan protocols for low contrastapplications make low radiation exposure possiblewith the Aquilion ONE. The example of the coronaryCTA in Figure 5 demonstrates the wide range in con-trast. In perfusion studies of the brain discrimination

between locations differing by just afew HU is also needed because the con-trast agent will dissipate in the entirevolume of the brain, thus producingrather small differences in HU levels.

Temporal resolutionWith the Aquilion ONE the scanning

time for volumes up to 16 cm is notdetermined by the combination ofrotation speed and pitch, but solely byrotation speed. Angiography and car-diac studies require fast rotation speedsof 350-600 ms in order to minimizevascular motion artefacts. Perfusionstudies call for slower rotation speedsof 750 ms to 1 s because of 30% moreprojections during the same time forraw data acquisition for image qualityimprovement. With the volume snap-shot of the organs fast rotation speedsare no longer needed in certain studies.

21

Fig. 2: 3D reconstruction of abdominal angiography with iso-phase contrast agent filling of all vessels (Aquilion ONE).(Courtesy of PD Dr P Rogalla, Charité Berlin, Germany)

c d

f g

In CT angiography (CTA), even a rotation time of onesecond is short enough to "freeze" all vessels with-in the scan volume. The 1-2 mm wide vessels con-trasted in iso-phase maximum will be visualizedwithout any breaks. Diagnostic studies of very smallvessels, e.g. the coronaries, are hampered if the con-centration of the contrast agent at the end of thebolus transit time is too low and if helical MSCT isemployed.

Half reconstruction or multi-segment recon-struction can be applied for coronary artery studies.With the Aquilion 64 in helical mode rotation speedand pitch are matched to the prognostic heart rateof the patient. For optimum temporal resolution acertain number of data segments will be employed,depending on the heart rate. In the Aquilion ONE therotation speed of 350 ms, 375 ms or 400 ms will also be matched to the heart rate and number ofsegments, but without the pitch and its side effects.For a heart rate of 60 bpm, i.e. an R-R interval of1,000 ms, a 350 ms rotation will expose 35% of allR-R phases. The time interval of the 350 ms expo-sure time will be gated by the R-signal to the adjustable cardiac phase range. With increasingheart rate two, three, four or five data segmentsfrom several consecutive beats will be used for multi-segment reconstruction (Figure 4). Minimumtemporal resolution will improve proportionally to


22

b

40

5

4

3

2

1

060 80 100 120 140

heart rate (bpm)

Num

ber

of d

ata

segm

ents

Fig. 4: Number of datasegments in multi-segment reconstruction for Aquilion ONE,depending on the heart rate

Fig. 3: Low dose phantom test with circular disks of 2-15 mm diameter, each with 0.1%, 0.3%, 0.5% and 1% contrast for a) Aquilion 64 and b) Aquilion ONE. Both CT scanners discern the disks at the various contrast steps on comparable levels. (Test protocol: 120 kV, 100 mAs, FC 43, 12 mm slice)

a

87 ms, 58 ms, 44 ms and 35 ms respectively and willmatch the faster motion of the heart. Here each datasegment will be adjusted to an identical cardiacphase in order to generate correct vascular super-position of the consecutive cardiac cycles. Radiationexposure increases with the number of segmentsand the number of rotations. On the other handcompared with a heart rate of 50 bpm, due to theshorter R-R interval the pulsed exposure time perone cardiac cycle at 100 bpm will be reduced for thesame cardiac phase percentage, thereby reducingexposure.

Cardiac action already undergoes real-time monitoring during the scanning interval. In case ofarrhythmia, extrasystole or excessive changes inheart rate the tube is turned off and the cyclerestarts with the next R-gating signal. The user mon-itors, corrects or deletes the reconstruction timeranges in each R-R cardiac cycle with the ECG Editorto avoid any loss in image quality due to cardiacdysrhythmias. In extreme case only one “normal” R-R cycle can be retrospective selected for the halfreconstruction.

Any discussion of data consistency from severalR-R cycles in multi-segment reconstruction shouldtake into account the fact that in helical scanningor step and shot mode 10-15 cardiac cycles (de-pending on the heart rate) will affect the image.Since the curved reformatted vessels are computedbased on the cardiac cycles, the Aquilion ONE notonly offers the benefit of a heart rate adapted tem-poral resolution of 35-175 ms (for 1-5 segments)but also that just a small number of cardiac actionsis needed for the complete set of 3D data. Partial

volume artefacts and step artefacts after helical or”step and shoot“ scanning are precluded. CurvedMPR reconstruction of the LAD artery from just oneheartbeat of the patient at a heart rate of 58 bpmand with a temporal resolution of 175 ms will yielda representative result (Figure 5).

SummaryThe spatial image voxels and the data acquisition

time are image quality elements of dynamic volumeCT. Even when looking at dose equivalency, high andlow contrast resolution of the Aquilion ONE, the firstdynamic volume CT scanner, compare favorably withthe results of the Aquilion 64. The volume snapshotwithin less than 200 ms of a whole organ allowsfunctional studies. Overbeaming is reduced pro-portional to the larger axial width of the detectors.Unnecessary overranging is avoided by selectivechoice of the axial scan width. After the scout scanthe number of detector rows is adjusted between 80to 320, depending on the measured size of the organ.Overscanning of the region scanned due to scan stopdelay is possible only in helical mode but is ruled outin dynamic volume scan mode. Compared with thehelical scan of a 64 MSCT and its standard pitch of0.2 for cardiac scanning, the lack of oversampling indynamic volume CT reduces radiation exposure by80%. This example demonstrates the ability of theAquilion ONE to employ this dose reserve in cardiacand perfusion studies. The dimension of a temporalresolution of > 35 ms and a spatial voxel resolution< 0.5 mm open up new horizons for 4D accuracy indiagnostic radiology, including the diagnostic studyof very small changes in tissue density.

1CT Systems Division

Toshiba Medical Systems CorporationTokyo 113-8456, Japan

2 Department of Radiology, CharitéUniversity Medicine Berlin, Campus Charité Center, 10117 Berlin, Germany

23

Fig. 5: Curved reconstruction of an LAD coronary artery (Aquilion ONE). Size as well as HU density of the plaque composition can be assessed even in low contrast levels. (Courtesy of Dr A Lembcke, Charité Berlin, Germany)

The advent of multislice computed tomogra-phy (MSCT), initially with four rows of detec-tors, and its widespread introduction into clini-cal practice barely eight years ago provided newopportunities in non-invasive cross-sectionalcardiac imaging, particularly in diagnostic stud-ies of the coronary arteries. Numerous studiesdemonstrated the potential inherent in MSCT in di-agnostic investigations of coronary artery disease,in particular for patients with low pre-test proba-bility of disease, low heart rate, and low calciumscore. The principal benefits of multislice helicalscanning are primarily due to improved spatial andtemporal resolution combined with ECG gating ofthe acquired data. Continuing development ofscanner technology resulted in thinner collimation

Case 1 Fig. 1a-d: Normal right coronary artery in 3D, MPR and MIP

with slice thickness in the sub-millimeter range aswell as faster rotation speed. This in turn led tosteady improvement in spatial and temporal reso-lution while the thicker detectors ensured largervolume coverage. However, in a 64-slice MSCTscanner the 32 mm wide detector (64 x 0.5 mm)cannot cover the entire heart. Thus, complete cov-erage requires continuous movement of the table

A Lembcke1, P A Hein1, J Mews1, J Blobel2, P Rogalla1

Cardiac Imaging with the320 Detector Row CT


24

1 Department of Radiology, Charité

University MedicineBerlin, Campus Charité Center

10117 Berlin, Germany

2Toshiba Medical Systems

Hellersbergstraße 441460 Neuss

Germany

a

b

c

d

which is realized either by 1) helical scanning withcontinuous table feed – a mode primarily employedin coronary contrast CT angiography with retro-spective ECG gating, or by 2) incremental scanningwith discontinuous table feed – a mode primarilyemployed in coronary calcium scoring withprospective ECG gating. Depending on the scanningmode selected, there will be various limitations.Helical scanning with retrospective ECG gating al-lows for image reconstruction at any point in timewithin the R-R interval and improves effective

temporal resolution by multi-segment reconstruc-tion. However, since high data density is mandato-ry (i.e. high degree of oversampling with multipleoverlap of the slices) a low pitch (usually about 0.2)is required. Images with multiple overlap and con-tinuous exposure over the entire cardiac cycle

25

a

Case 2 Fig. 2a-b: Minute atheromatous wall degeneration of RIVA in 3D, MPR, including soft plaque

visualisation with SurePlaque

b

Case 3 Fig. 3a-b: RCA with

medium stenosis(medial) and

implanted stent(distal)

cause the major drawback of this acquisition mode:significant radiation exposure. Therefore, it wassuggested to replace overlapping helical acquisi-tion with continuous exposure by non-overlappingincrementation with selective exposure within thecardiac cycle.

However, incremental scanning with prospec-tive ECG gating does not allow multisegment re-construction which is often highly desirable inhigher heart rates. In addition, various partial vol-ume data sets have to be "concatenated" and fusedinto a single volume data set. In low heart rateswith regular rhythm this will yield acceptable im-age quality, in higher heart rates and arrhythmias,however, artefacts are to be expected, resulting inblurred or stepped vascular contours due to differ-ences in the magnitude and speed of the coronaryartery deflection.

These problems have been solved by 320-slicecomputed tomography. The planar detector fittedwith 320 rows of 0.5 mm detectors and a coverageof 16 cm along the z–axis of the patient allows forthe acquisition of a high resolution data set of theentire heart in a single rotation. The benefits of thistechnology are obvious: by covering the entire or-gan a complete volume data set of the heart can beacquired in one heartbeat and without reposition-ing of the table. Thus, the limitations of helical andincremental scanning, i.e. the fusion of potentiallyincongruent raw data originating from differentcardiac cycles, are overcome. This helps to avoidartefacts in the reconstructed images, particularlythose obtained in patients with arrhythmias. Unlikehelical scanning, 320-slice CT scanning acquiresdata without overlap - a key precondition for re-ducing radiation exposure. In patients with a low


26

a

b

heart rate and stable cardiac rhythm, it is thus pos-sible to acquire data in one heartbeat by selectiveexposure within the cardiac cycle (usually 70-80%of the R-R interval); in ideal circumstances thismeans an effective dose of about 3 mSv. Scanningis performed with prospective ECG gating. It shouldbe emphasized that even under the most unfavor-able conditions the very low radiation exposurepermits repeat scans – although the resulting ef-fective dose is doubled, its value of 6 mSv is still be-low the current standard dose in a CT study of theheart. It should also be noted that even withprospective ECG gating in 320-slice mode the da-ta can be acquired across several cardiac cycles,thus permitting image computation with the mul-tisegment reconstruction algorithm. The latter in-creases temporal resolution in order to avoid mo-tion artefacts in higher heart rates and is thus afurther essential improvement over the 64-slice CTscanner. Nevertheless, it has to be emphasized thatdata acquisition across several cardiac cycles forthe purpose of multisegment reconstruction willincrease the effective dose.

The short acquisition time of the raw data –which may be in the second to sub-second range –also reduces significantly the required amount ofintravascular contrast agent. In patients with nor-mal cardiac function and visually monitored bolustracking (the scan is manually started as soon asthe contrast agent becomes visible as it enters the

left heart), a volume of 50 ml of contrast agent anda flow rate of 5 ml/sec will almost always result ingood contrast of the left cardiac cavities, aorta andcoronary arteries.

Our initial experience with more than 100 pa-tients indicates that the Aquilion ONE generatesoutstanding image quality (Figures 1-4). In all thepatients we studied the information gained fromthe data acquired contributed to further clinicaldecision making – the failure rate (the number ofnon-diagnostic scans) tended toward zero.

A further, altogether new area of application innon-invasive diagnostic cardiac imaging is my-ocardial perfusion imaging by computed tomogra-phy. In dynamic scanning mode the CT scanner isable to record the volume data of the entire heart,either continuously during a specific interval or in-termittently in certain time intervals. Future stud-ies will have to investigate the accuracy of thismode in demonstrating myocardial perfusion dis-orders, its relevance in clinical routine and in par-ticular its significance compared to competingimaging modalities.

Alexander Lembcke MDDepartment of Radiology

Charité, University Medicine Berlin, Campus Charité Center

Charitéplatz 1, 10117 Berlin, Germany

27

Case 4 Fig. 4a-b: Patient with a sequential venous bypass (3D and MPR)

a b

Fig. 1: Aquilion ONETM

calcium scoring allowsdetailed examination of

coronary calcium andplaques. Color coding inall views combined with

volume measurementsfacilitates a quick and

accurate assessment ofatherosclerotic lesions.

Dynamic volume CT imaging or 4D CT imag-ing has attracted much attention recently. Theworld’s first dynamic volume CT scanner with 320detector rows covering a scan length of 16 cm hasjust been introduced by Toshiba as Aquilion ONETM

(see article “The History of CT” in this issue). Thiswide coverage enables scanning of the heart or

R IrwanH B K de Vries

A brief summary of patientdoses of dynamic volume CT


28

brain within one rotation, eliminating the need forhelical scanning.

The aim of this paper is to clarify advantages ofcardiac applications with “one-beat whole heartimaging” in clinical cases. Particularly, the dose is-sues in several main cardiac applications will be pre-sented.

Roy Irwan, PhD, Henk B K de Vries,

Toshiba Medical Systems Europe BV,

Zilverstraat 1, 2718 RPZoetermeer,

The Netherlands

Case 1A 62-year-old male patient with a family his-tory was admitted to the hospital with symp-toms of suspected Coronary Artery Disease(CAD). The patient was referred to an exam-ination for calcium scoring, in the first case.The patient was scanned on Aquilion ONETM

scanner using an examination protocol shown inTable 1. The patient had a heart rate of 75 beatsper minute (bpm) during the CT scan.

Table 1: Examination protocolfor cardiac calcium scoring.

Scanner Aquilion ONEScan area HeartScan length 120 mmRotation time 0.35 sHeart rate 75 bpmkV 120mA 300Temporal resolution 175 msSpatial resolution 0.35 mmPatient dose 2 mSv

29

Fig. 2a: Volume rendering of the coronary CTA datasets providing very accurate visualization of coronary arteries.Fig. 2b: Segmentation of the complete coronary tree allowing the precise examination of all coronaries.Courtesy of Dr. K. Katada, Fujita Health University, Aichi, Japan

Examination Synchro- Rotation Tube Tube Scan Scan Dose Patient nization time (s) voltage current coverage time modulation dose

(kV) (mA) (mm) (s) (mSv)

Calcium Prospective0.35 120 300 120 0.35 Pulsed 2scoring triggering

CTA coronary Retrospective0.35 120 400 120 0.35 Pulsed 2.8arteries gating

LV function Retrospective 0.35 120 400 120 1.4 Modulated 5gating

Table 3: Typical acquisition and reconstruction characteristics of 60 bpm cardiac CT examinations onAquilion ONETM.

Case 2

Table 2: Examination protocol for coronary angiography using

multisegmental SUREProspective Cardio.

Scanner Aquilion ONE

Scan area HeartScan length 120 mmRotation time 0.35 sHeart rate 86 bpmkV 120mA 400Number of segments 3Temporal resolution 58 msSpatial resolution 0.35 mmPatient dose 8 mSv

Patient doses for cardiac applications

Patient dose depends strongly on the type imageacquisition. In turn, the type of image acquisitionwould depend on the clinical requests by a medicaldoctor. For example, CT coronary angiography re-quires excellent spatial and temporal resolutionwhereas the assessment of the anatomy of pul-monary veins and the left atrium has sufficient witha modest setting. Generally, the higher the require-ments for image quality, the longer scan time andthe higher patient dose.

Effective patient dose, expressed in mSv, can bederived from the CT dose index (CTDI), expressed inmGy, and dose-length product (DLP) expressed inmGy.cm. Patient dose from cardiac CT coronary an-giography is relatively high, mainly due to the needto acquire the heart more than one cycle. However,using ECG triggered dose modulation the dose canbe reduced down to approximately 3 mSv. In con-trast, patient dose from acquisitions for calciumscoring purposes may be as low as 2 mSv.

We report two cases representing calcium scor-ing and coronary angiography examinations.

Figure 1 shows Toshiba Calcium Scoring graphi-cal user interface that enables a fast and accuratedefinition of a patient’s calcium burden. Both Agatson and volume scoring are available to assurethe most accurate assessment.

A volume rendering of the coronary datasets isshown in Fig. 2a which allows you to determine theseverity of a suspicious coronary artery at a glance.

The accurate segmentation tool automaticallysegments the complete coronary tree allowing theprecise examination of all coronaries down to themost distal segments (Fig. 2b).

SummaryIn this paper, the technical requirements of car-

diac dynamic volume CT imaging and some mainclinical applications have been presented. CT-an-giography of the vascular system is one of the mostfrequently employed examinations in CT. Contrast-enhanced scanning of the cardiac cavities and coro-nary arteries is now possible with one single rotation.

Patient dose should always be related to the needof image acquisition and image quality. Typical ac-quisition and reconstruction parameters for someclinically established cardiac CT applications aresummarized in Table 3. With Aquilion ONETM and us-ing three segment reconstruction, we can achieve atemporal resolution of 58 ms. This combination oflow-dose and better temporal resolution drasticallyimproves diagnostic quality and patient safety of CT.

A 55-year-old female patient with a history ofhypertension was admitted to the hospital withsymptoms of suspected coronary artery stenosis.The patient was scanned on Aquilion ONETM scan-ner using an examination protocol shown in Table2. The patient had a heart rate of 86 bpm during theCT scan. Multi segmental SUREProspective Cardioreconstruction has been used in which threesegments were needed to match the patient’s heartrate.

a b

Fig. 1: Toshiba Aquilion ONE, 320-detector row CT installed at the radiology department at Charité

University Hospital. Neuroradiology CT group (left: the author, right: G Bohner, MD).

Since November 2007 our department hasbeen equipped with the latest Toshiba dynamicvolume computed tomography scanner featuring320 detector rows - the Aquilion ONE. It is thethird clinical dynamic volume CT scanner worldwideand the first in Europe. The increased detector widthof 16 cm, unique in CT technology so far, enables si-multaneous imaging of large volumes. Thus, duringone single rotation structural imaging data of thewhole-brain can be acquired. But not only morpho-logical information can be gathered quickly. Themain advantage of this new-generation CT scanneris the possibility to acquire physiological informa-tion of the whole-brain. Continuous scanning en-ables dynamic time-resolved imaging of the in-tracranial vasculature (4D-CT angiography/4D-CTA)and CT brain perfusion (CTP). These options are like-ly to have a considerable impact on computed to-mography neuroimaging since some severe limita-tions of conventional multislice CT imaging havebeen overcome. Due to the limitation of con-ventional detector widths to 32 mm (64 detectorrows x 0.5 mm) whole-brain coverage cannot beachieved, a fact that reduces CT perfusion to partialbrain coverage and renders 4D-whole-brain CTAimpossible. Below, some information about the pro-tocols used in our department at Charité Universi-ty Hospital, Berlin, will be provided and some of ourexperiences with this long anticipated and excitingnew CT technology will be illustrated.

We use single rotation volume acquisition techniques for unenhanced and post-contrast cra-nial CT scans as well as for cervicocranial CT an-giography (3D-CTA). In contrast to conventionalspiral mode multislice scanners, cervicocranial CTAcoverage is performed incrementally. Usually threesteps are required to cover the volume betweenaortic arch and the vertex. Bolus timing can becalculated with a test bolus or performed manual-ly by a low-dose dynamic (SUREStart) scan at the levelof C4.

For the dynamic, time-resolved imaging meth-ods, 4D-CTA, CTP and a combination of both (4D-CTA/CTP) protocols with both intermittent and con-tinuous scan components are used. Below, thecombined protocol will be addressed briefly.

E Siebert

Initial Experiences with the 320 Detector Row CT in Neuroimaging


30

Fig. 3: Physiological sequelae of intracranial 4D-CTA images from early arterial via arterio-venous to venous phase of contrast passage.

Sagittal, bone-subtracted 4D-CTA whole-brain MIPs.

Fig. 2: Unenhanced, single-rotation, volume cranial CT consisting of 320 x 0.5 mmaxial sections. This allowsfor high-quality multipla-nar reformation.

For the 4D-CTA/CTP protocol, following test bo-lus-assisted calculation of circulation time, a 50second total duration protocol of combined inter-mittent and continuous scanning is used. Continu-ous scanning is performed to gather the complete4D-CTA information during the first pass of thecontrast media bolus as well as the essential infor-mation for the whole-brain CTP. Intermittent scansbefore the continuous scan block are used to con-struct a mask for bone-subtraction which is indis-pensable for adequate 4D-CTA post-processing. In-termittent scans after the continuous scan blockadd information to the CTP as with conventionalscanners. The bolus of iodinated contrast agentamounts to 50 ml.

Dynamic scanning is performed using an 80 kVand 100 mAs protocol to keep radiation exposureat a level comparable with conventional CTPinvestigations. The resulting dose-length productis 2355,4 mGy*cm. Multiplied with the ICRP-factor(k = 0.0023 mSv/(mGy*cm) for the head) this shouldresult in a calculated effective dose of 5,4 mSvwhich is in line with Toshiba’s phantom measure-ments where radiation exposure for the dynamicwhole-brain 4D-CTA/CTP combination was 6.4 mSv.

31

According to our clinical experiences motion arte-facts are substantially reduced when using the volume CT mode and 3D-CTA protocols. This appliesespecially to uncooperative patients, who are a con-siderable group within the emergency patient popu-lation, and represents a significant advantage overconventional incremental acquisition (CCT) and spi-ral acquisition of cervico-cranial 3D-CTA.

The CCT results in a single volume of 320 x 0.5mm axial slices that can be reformatted as required(Fig. 2). So far, dynamic volume CT has mainly beenperformed for vascular trauma, acute stroke, chron-ic cervico-cranial vascular insufficiency as well asveno-occlusive disease. Figure 3 illustrates thequality of information gathered by such a 4D-CTAprotocol. As even these few examples show, thisnew 320-detector row CT scanner generation virtu-ally opens up the fourth dimension for neuroradio-logical evaluation of the brain. The preliminary eval-uation of shunting vascular disorders has alreadybeen performed successfully.

Figure 4 illustrates an arterio-venous malforma-tion within the basal ganglia which is fed by en-larged lenticulostriate branches of the middle cere-bral artery. CT-based neuroimaging was performed

due to persistent headaches of the patient. Theaneurysmatic nidus is well shown as is the deep ve-nous drainage of the AVM. Both findings provideimportant information to assess the probability ofintracranial hemorrhage and therapeutic proce-dures. A novel feature of this new scanner genera-tion is the possibility to assess acceleration of cere-bral circulation time due to arterio-venousshunting. Already in the arterial phase early venousdrainage via the internal cerebral vein and thestraight sinus is evident whereas other venousstructures, e.g. the superior sagittal sinus, are notyet opacified. This broadens the diagnostic spec-trum of CT-guided diagnosis substantially and ismost likely beneficial for evaluation of diseases withaltered hemodynamics. Dynamic whole-brain CTimaging does not only allow assessment of circula-tion time changes in shunting vascular disordersand venous arterialisation, but also delay of venousoutflow in the setting of veno-occlusive disease, es-pecially in cortical vein thrombosis, a subtle diag-nosis previously confined to invasive catheter an-giography. All these neuroradiologically importantissues can now be addressed directly and dynami-cally by whole-brain 4D-CTA.


Fig. 4: Arterio-venous malformation within thebasal ganglia fed by lenticulostriate branches of

the middle cerebral artery. Note the highly irregu-lar and lobulated appearance of the aneurysmatic

nidus. The mid-arterial image shows venous opacification of the internal cerebral vein and the

straight sinus. Other venous structures, such as thesuperior sagittal sinus, are not yet visible.

32

Comprehensive neuroimaging of cerebrovascu-lar insufficiency and namely imaging-guided diag-nosis of acute stroke will most probably benefitfrom the dynamic whole-brain imaging functional-ities provided by 320-detector row CT. The sensitiv-ity of CT perfusion will almost certainly increase, es-pecially when lesions in infratentorial or higherfronto-parietal locations are the cause of the neu-rological deficits. Whether this new quality of in-formation will be of clinical importance, however,remains to be determined. As illustrated in Figure 5,the parameter maps of CT perfusion profit greatlyfrom the high spatial resolution, not only in the ax-ial plane but also in the z-direction. The voxel sizeof 0.5 mm along the z-axis by itself is an importantnew feature and particularly meaningful since un-til recently it was impossible to reap the benefits ofsuch through-plane resolution for the whole-brainfrom the cerebellar tonsils to the motor and so-matosensory cortex. This near-isotropic data allowsfor elaborate post-processing with all its potentialsand options the radiologist is used to from multi-slice CTA (Fig. 6).

However, the quantity of data this new CT scan-ner generation has to gather in order to be able toprovide the new quality and dimension of informa-tion increases substantially. Comprehensive neu-roimaging, including unenhanced CT, 4D-CTA/CTPand cervico-cranial 3D-CTA, amounts to approx.10,000 DICOM images that have to be processedand stored within a reasonable time for the new

technology to be useful in clinical routine. Thatmeans the new 320-detector row scanner has highinfrastructre requirements in terms of network con-nections and PACS.

In short, 320-detector row CT opens up thefourth dimension for comprehensive neuroimagingof the whole-brain. Isotropic, dynamic whole-braindata acquisition allows for unsurpassed and un-precedented quality of post-processing, resulting insimultaneously acquired high-class 4D-images ofthe intracranial vasculature and perfusion mapscovering the whole-brain. The new quality of infor-mation, however, requires increased data quantities,a fact which poses a challenge to network and PACSinfrastructure. Dynamic whole-brain imaging by320-detector row CT is an exciting and very promis-ing method for comprehensive neuroradiolo-gicalassessment of cerebro-vascular diseases althoughits clinical value for specific disease entities stillneeds to be determined in further studies.

33

Fig. 5: Generation of CT perfusionmaps with the Vitrea 4.0 software(Vital Images, Minnesota, USA).The resolution of 0.5 mm alongthe z-axis allows for multiplanarreformation of the whole-brainperfusion maps without loss ofinformation.

Fig. 6: Surface rendered image of a physiological cerebral blood flow (CBF) map to illustrate one of the various novel options

of CTP data post-processing

Eberhard SiebertDepartment of Neuroradiology Charité – University Medicine BerlinCharitéplatz 110117 BerlinGermany

The gold standard for the investigation ofocclusive peripheral and renal arteriopathies inischemic nephropathy and/or renovascular hyper-tension has traditionally been classic arterio-graphy. However, this technique is relatively inva-sive, and in recent years has been used solely forvisualization during revascularization procedures. Indiagnostic workup where endovascular or surgicalmanagement is envisaged, arteriography has beenreplaced by magnetic resonance angiography (MRA)and computed tomography angiography (CTA),reliable imaging modalities which allow for vascularmapping comparable to classic angiography.

Although CTA results have been excellent sincethe advent of 16- and 64-slice multidetectors, radi-ation exposure and the intravenous (i.v.) iodine con-trast agent associated with the procedure oftenmake contrast MRA a more appealing option for thepatients who are often polyvascular, diabetics orsuffer from renal insufficiency.

A recent report of nephrogenic fibrosis being in-duced by gadolinium in patients with moderate tosevere renal insufficiency underscores more thanever the need to realize high quality, contrast-freevascular imaging by MRA, and to rethink the explo-ration strategy for these peripheral vascular lesions.

Innovative non-contrast MRA techniques knownas FBI (Fresh Blood Imaging) and Time-SLIP (Time-Spatial Labeling Inversion Pulse) by Toshiba havebeen available for clinical use for several years inJapan and for nearly one year in France, using thenew Toshiba 1.5 T MRI systems Vantage and Vantagepowered by Atlas. Both systems offer a high qualityand a totally safe alternative for pre-therapy as-sessment of occlusive arteriopathies in the periph-eral and renal arteries.

Occlusive arteriopathy in thelower extremity

This common pathology, which is associated witha high level of morbidity, requires precise informa-tion on the degree of stenosis, its localization andthe extent of the lesions prior to revascularizationprocedures.

Although echo-enhanced Doppler sonographyprovides morphological and hemodynamic informa-tion, the examination is lengthy, complex, often in-complete and does not map the area of interest asgood as classic angiography. Nevertheless, it is stillmany surgeons’ modality of choice. CTA has emergedas an efficacious tool combining outstanding spatialresolution with high-speed acquisition, thus reduc-ing the required amount of contrast agent andavoiding venous return at the popliteal artery trifur-cation. In the evaluation of stenoses, CTA has a sen-sitivity and specificity of approximately 95%. Al-though visualization of calcifications is useful, itsometimes interferes with the evaluation ofstenoses.

The major drawback of CTA is radiation exposureand its inherent need for iodine contrast agentswhich may induce or exacerbate nephropathy.

Contrast-enhanced MRA has revolutionized pa-tient workup since, if carried out correctly, it pro-vides quality images on a par with those generatedby classic angiography, and also with a sensitivityand specificity of approximately 95%.

The main technical difficulties in CTA can besummarized as follows:• overestimation of the degree of stenosis • artefacts occasioned by calcification or metal

(stents) • venous contamination • impregnation of the tissue with gadolinium.

FBI should therefore be evaluated against CTA orgadolinium-MRA. This technique constitutes a FASE(fast advanced spin echo) sequence and uses an ECGgated half-Fourier acquisition in T2.

Two acquisitions are synchronized by ECG asfollows: (a) in systole, where only the veins exhibit ahypersignal since arterial flow is too rapid; and (b)in diastole, where both the veins and arteries exhib-it a hypersignal.

The automatic subtraction of the two imagesallows for visualization of the arteries alone. Thistechnique may overestimate the degree of stenosisand may present artefacts due to the presence ofcalcium, metal (stents), peristalsis around the iliac

I ParientyF Jouniaux

Fresh Blood Imagingand Time-SLIPBreakthrough techniques for non-contrast MRA investigations of peripheral and renal arteriesin patients with renal insufficiency

SPECIAL MRI

34

artery. Furthermore, it could be sensitive to patientmotion between the acquisitions of the two phasesas it leads to misalignment of the two images andthus incomplete subtractions.

The examination is performed in four successivecycles from the infrarenal aorta to the plantararcade and takes about 40 minutes in total on a Van-tage XGV system.

35

Case 1

82-year-old male patient with normal renalfunction who was referred for evaluation ofan incomplete stenosis of the right femoralartery suspected in echo-enhanced Dopplerscanning of the lower limbs.

After obtaining the consent of both the patientand the referring physician, we performedgadolinium-MRA as well as FBI. The three modalities yielded comparable re-sults for evaluation of the right femoral arteryocclusion, with good resumption of down-stream flow and collateral circulation via thedeep femoral artery. Owing to the presence ofnumerous calcifications, both MRA modalities

allowed for better visualization of vessal wallirregularities in the remainder of the arterialbed. Visualization of the popliteal artery trifurcationwas better with FBI than with CTA (possiblyowing to an injection timing problem in thispatient attributable to the slow flow rate ofcontrast agent through the peripheral arteries)or gadolinium-MRA, where the images werecorrupted by venous return. Due to overall tis-sue enhancement following the gadolinium in-jection the signal-to-noise ratio was poor.

CT angiography Gadolinium-MRA FBI

Comparative study of clinical cases

The cases described below involved the perfor-mance (at our imaging center) of either FBI in con-junction with CTA or contrast-MRA which was eitherrequested by the referring physician or was plannedfrom the outset because of renal insufficiency.

SPECIAL MRI

36

Case 2

67-year-old polyvascular male patient withnormal renal function who was referred forCT angiography scanning of the peripheralarteries and in whom we also performed FBIMRA with the patient’s consent.

The quality of the study was essentiallyidentical with the CTA from the infrarenal aor-ta to the popliteal arteries, but was far poorerat the level of the popliteal artery trifurcation,probably owing to patient movement between

acquisitions which occasioned incomplete sub-tractions and venous signal corruption. In or-der to avoid the generation of artefacts whichmay make the images difficult to interpret, thepatient must remain perfectly still during theprocedure.

FBI revealed numerous vessel wall abnor-malities in the iliac artery region consistentwith the calcifications detected on CT angio-graphy.

CT angiography FBI

37

Case 3

Male patient presenting with sensitivityproblems in the left leg as well as acutetrauma due to a traffic accident.

Multiple fractures of the pelvis and left femurand a femoral artery lesion, necessitating vas-cular surgery and total hip replacement ac-companied by osteosynthesis of the acetabu-lum and the distal femur. Two MRAs wereperformed with gadolinium and in FBI mode.

Both techniques yielded the same visualizationof the arterial axes. The metal artefacts weremore severe with FBI but following injection ofgadolinium artefacts were observed resultingfrom tissue impregnation and venous return inthe region of the left thigh. No significant lesion was observed which couldhave explained the symptoms.

MRA with gadolinium FBI

SPECIAL MRI

38

Case 4

65-year-old polyvascular male patientpresented with coronary pathology (sched-uled for stenting).

Stenosis of the left superficial femoral artery(detected on echo-enhanced Doppler sonog-raphy) and renal insufficiency. The patient al-so complained about pain in the left leg andfoot. Due to the patient’s renal insufficiency, awhole-body non-contrast MRA was per-formed. The peripheral arteries were investi-gated by FBI and the renal arteries underwenta Time-SLIP study (see below). The quality of the FBI study was good in allsegments. Complete occlusion of the left su-perficial femoral artery was observed withgood resumption of flow downstream andcollateral circulation via deep femoral artery.At the left popliteal artery trifurcation com-plete occlusion at the level of the middlethird of the anterior tibial artery was ob-served, with very sluggish flow in the firstthird of this artery. We also detected a sig-nificant short and dense stenosis at the ori-gin of the tibioperoneal trunk, with substan-tial reduction in downstream flow in theperoneal and posterior tibial arterial tree dueto this pathology. Simple vessal wall irregu-larities were detected in the right leg.

MRA without contrast agent

39

Case 5

70-year-old female polyvascular patientpresented with coronary artery disease andperipheral arterial occlusive disease (previ-ously studied in 2006 by CTA) with inter-mittent claudication.

No renal insufficiency was observed. Contrast-agent MRA and FBI were performed and theimages obtained were compared with the pre-vious angiography scans. The FBI examinationyielded satisfactory image quality in all seg-ments.

Due to motion artefacts in the other segments,the MRA results were meaningful only for theiliac arteries. Both modalities revealed a minor stenosis oneach external iliac artery with a good down-stream flow but more constricted in the left leg.This stenosis appeared larger on FBI and was ofthe same size on CTA and contrast-enhancedMRA.

MRA with gadolinium

CTA FBI

SPECIAL MRI

40

Case 6

59-year-old male patient presented withlower extremity pain and an atheromatousplaque visualized on echo-enhanced Dopplersonography.

A CTA study was performed, followed by FBIMRA. Both examinations yielded high imagequality results. CT angiography revealed numerous vessel wallcalcifications in the infrarenal aorta and thecommon iliac arteries. We also observed nu-merous wall pathologies, attributable to soft

atheromatous plaques. No significant stenosiswas observed, but the right superficial femoralartery exhibited a greater amount of plaque,with a collateral artery originating from thedeep femoral artery supplying the superficialfemoral artery further downstream. This collat-eral artery was more pronounced on FBI thanon CTA, whereas the deep femoral artery wasless visible. Furthermore, a larger plaque in theleft popliteal artery was much better seen onthe FBI images because of its calcification.

CTA FBI

41

Studies of the renal arteries The renal arteries are investigated in patients

with suspected renal hypertension and/or ischemicnephropathy and for whom endovascular or surgicalrevascularization is an option.

The main objective when revascularizing renalatheromatous stenosis is the preservation of renalfunction.

Atheromatous disease affects the renal arteriesdiffusely up to the most distal branches and in somecase revascularization fails to improve renal func-tion.

For bilateral stenosis of at least 60%, generallyone has to choose between the more common ther-apeutic options of angioplasty and stenting or leftsplenorenal and right hepatorenal bypass respec-tively, which are performed far less frequently. Therisk entailed by revascularization (obstruction, dis-section of the renal artery, renal infarction, deterio-ration of renal function) increases in those caseswhere atheromatous plaques involve the aorta andthe coronaries. Hence the diagnostic strategy in suchcases is of utmost importance.

Diagnostic imaging should delineate the severi-ty, extent and localization of the stenoses, visualizethe most distal arterial segments, detect all collat-eral renal arteries (which may arise anywhere be-tween the suprarenal aorta and the iliac arteries)and evaluate the renal parenchyma.

The main drawback of CTA is its need for the in-jection of iodine which entails a high risk of inducednephropathy. However, CTA provides outstandingspatial resolution and detecting calcifications can beuseful for stent implantation as well as for follow-ups after stenting.

Gadolinium-MRA is realized in frontal acquisitionmode so as to allow for visualization of the entire

aorta from its suprarenal segment down to the com-mon iliac arteries, with a large field of view. CTA de-tects ostial and proximal stenoses (which are mostcommon) with nearly 100% sensitivity and a speci-ficity of 75-100%, but visualizes the arterial trunksand distal branches poorly. Artefacts due to calcifi-cations and stents are also seen with this method.Until recently, before some gadolinium-based con-trast agents were linked to renal toxicity, gadolini-um-based contrast-enhanced MRA was considereda totally safe technique in patients with renal insuf-ficiency.

Time-SLIP (Time-Spatial Labeling InversionPulse), an innovative non-contrast MRA modalityavailable from Toshiba, allows for the imaging of se-lective vessels via prior marking (tag pulse).

3D acquisition is realized via a rapid sequence ofimages in T2.

A pre-saturation band is placed under the acqui-sition volume so as to separate the arterial and ve-nous blood flow.

A complete study entails axial acquisition for op-timal visualization of the distal segments of themain renal arteries and acquisition in the coronalplane for visualization of the entire abdominal aor-ta down to the common iliac arteries, in order to de-tect all collateral renal arteries. A third sequence isalso carried out in order to assess parenchyma sta-tus of the kidneys.

Clinical cases Case 1 was an examination of a healthy volun-

teer, on whom a complete Time-SLIP investigation ofthe renal arteries was carried out. Cases 2-4 showpatients suspected with renal stenosis.

Case 1

Examination of a healthy volunteer permit-ting complete evaluation of renal vascularstatus.

The Time-SLIP modality allows for accurateimaging of the distal renal arteries, as well as therenal parenchyma and the entire aorta down tothe iliac arteries.

Time SLIP - axial acquisition Time SLIP - coronal acquisition

SPECIAL MRI

42

Case 2

A 35-year-old female patient re-ferred for MRA evaluation of herhypertension. The study consistedof a gadolinium-enhanced MRA anda Time-SLIP, in axial acquisition cen-tered on the renal arteries. Compar-ison of both modalities demonstrat-ed that the distal renal arteries werefar better seen on Time-SLIP. No sig-nificant abnormality was observed.

Time SLIP - axial acquisition

Case 3

A 68-year-old male patient with poorly con-trolled hypertension who presented withacute renal insufficiency. Echo-enhancedDoppler sonography provided no useful infor-

mation in this case and thus diagnostic con-trast-free MRA was performed. For each kidney,Time-SLIP revealed one principal renal arteryand a collateral upper polar artery of sufficientlumen. We observed a significant ostial steno-sis of the main right and left arteries with sat-isfactory preservation of distal flow; the distalarteries were well depicted. After seeking anexpert opinion and despite the patient’s pooroverall vascular status and the presence ofslightly atrophic renal parenchyma, the patientunderwent endovascular revascularization dur-ing which both main renal arteries received astent.


Case 4

Same polyvascular patient as in the FBI case3 above. Because of his renal insufficiency,only Time-SLIP could be used to explore his re-nal arteries.

This investigation revealed a right main arterywith atheromatous ostial plaque with anirregular lumen size but no significant steno-sis; the downstream flow and depiction of the

distal branches were both satis-factory.


43

Case 4

A significant ostial stenosis with substantiallydiminished downstream flow was detected in

the main left artery and inferior polar artery. Asubstantial number of atheromatous plaques

were detected in the suprarenaland particularly in the infrarenalvessels. The renal parenchyma was nor-mal. This patient was explored andtreated by endovascular stentingof the ostial stenosis of the mainleft artery.

OutlookStudies of other lesions in these vessels (e.g.

aneurysms, dissections, fibrous dysplasias) could al-so be realized and other applications seem promis-ing, particularly arterial investigations of the handsand feet using FBI, as well as Time-SLIP explorationof the portal system and the pulmonary arteries,coronary imaging and dynamic imaging of thecarotid arteries.

Prospective randomized studies are needed in or-der to evaluate the sensitivity and specificity ofthese modalities in the detection and assessment ofperipheral arterial stenoses.

Once the operator has acquired a modicum of ex-perience with these modalities, studies of consis-tently high quality can be realized and the mainartefacts avoided.

Hence, based on the clinical cases presented here,with Toshiba’s non-contrast imaging modalitieswhich can successfully perform MRA – fresh bloodimaging (FBI) and Time-SLIP – the results are com-parable to those obtained by CTA and gadolinium-MRA.

When combined with Toshiba’s MRI Vantage andAtlas scanners, these modalities appear to be suffi-ciently reliable for the study of peripheral and renalarterial lesions in patients with moderate to severerenal insufficiency. These modalities represent a sig-nificant breakthrough since in these patients, thestandard diagnostic options are barred due to therisk of iodine-induced nephropathy associated withCTA and the risk of irreversible gadolinium-inducednephrogenic fibrosis associated with MRA.

References- Vascular and interventionnal Radiology, Karim VALGI (Saunders)- Angiographie par resonance magnétique, Philippe DOUEK, J.P. LAIS-

SY, C.LIM, H.TRILLAUD (Masson)- Imagerie des artériopathies des membres inférieurs hors Echo-

Doppler, Serge Willoteaux, (sang, thrombose , vaisseaux vol.18 n°5mai 2006 )

- Aortoiliac and renal arteries : prospective Intraindividual Compari-son of contrast-enhanced Three-dimensionnal MR Angiography andmulti-detector Row CT Angiography, J.K. WILLMANN, (Radiology2003;226:798-811)

- 16 Detector Row CT Angiography in peripheral Arterial Disease: Ran-domized Controlled Trial, M.C.J.M. KOCK, (Radiology, Novem-ber1,2005; 185,5: 1261-1267)

- DSA versus Multi-Detector Row CT Angiography in peripheral arte-rial disease Randomized Controlled Trial, M.C.J.M. KOCK, (Radiolo-gy,November 1 ,2005 237(2) 727-737)

- Quantitative Vascular Measurements in Arterial occlusive Disease, H.OTA, (Radiographics, September 1 2005 25(5) 1141-1158)

- Aorto-Iliac and lower extremity arteries Assessed with 16 DetectorRow CT Angiography: Prospective Comparison with Digital Sub-straction Angiography, J.K. WILLMANN, (Radiology September 12006 236(3) 1083-1093)

- Peripheral Arteries in Diabetic patients: Standart Bolus-Chase andTime-Resolved MR Angiography, G.ANDREISEK, (radiology, Decem-ber 19 2006)

- Vessel Wall Calcifications and Multi-Detector Row CT Angiographyin patients with Peripheral arterial disease. Effect on Clinical Utilityand Clinical predictors, R.OUVERDIJK, (Radiology, November 12006, 241(2) 603-608)

- Imaging Peripheral Arterial disease : a randomized controlled trialcomparing contrast enhanced MR Angiography and Multi-DetectorRow CT Angiography, R.OUVERDIJK, (Radiology, Sptember 12005,236(3), 1094-1103)

- Contrast enhanced MR Angiography of the renal arteries; BlindedMulticenter crossover comparison of Gadobenate Dimeglumine andGado Pentetate Dimeglumine, M.PROKOP, (Radiology February 12005, 234(2) 399-408

Dr Isabelle ParientyF JouniauxCentre d’Imagerie du Bois de Verrière48, rue du Colonel FabienF- 92160 AntonyFrance

IntroductionHigher expectations in routine echocardiogra-

phy, new quantification and visualization techniquesand the ever increasing demand for workflow andergonomic solutions present many challenges to thedevelopment of an echocardiography system. In par-ticular interest in 4D ultrasound is driving changesto system architecture, transducer design and rawdata processing capability.

Toshiba’s development of ArtidaTM required inno-vation in all aspects of ultrasound system design. Itwas very important to have good clinical input be-fore developing this new technology. Establishing aMedical Advisory Board and user groups were themost important first steps. Strong demand for imag-ing performance, advanced applications, workflowinnovation and ergonomics drove the developmentof a new range of technologies that significantly im-pact system performance.

State-of-the-art transducer technology

Conventional transducers feature a row of trans-ducer elements which generate a two-dimensionalimage. In recent years transducers with subdicing ofthe elements and electronic switching to vary the re-ceive element characteristics known as 11⁄2 D array(or sometime matrix) transducers have been used tominimize beam thickness in 2D scanning. Also insome applications 3D and 4D scanning has been

achieved by rapidly sweeping a 1D array transduceracross a volume mechanically. However, frame ratesand footprint have not been satisfactory for cardiacapplications in such transducers.

In order to generate high-quality four-dimen-sional imaging with excellent image quality, tempo-ral resolution and control flexibility a true matrixtransducer approach is required. By being able totrans-electronically control the excitation of a two-dimensional array of ceramic elements rapidly overtime a 4D wave pattern can be created. Similarly a4D volume can be created by carefully processingthe signal received over this array.

Furthermore, ergonomic requirements dictatethat such a transducer be compact and lightweight.In particular the length of transducer must be min-imized in order to make apical imaging easier. Lim-ited space between patients’ ribs dictates a smallfootprint.

To achieve these requirements a new class oftransducers is required. SmartFocus technology wasdeveloped specifically to meet these requirements.New piezo-electric materials provide greater sensi-tivity and resolution by increasing the bandwidth ofthe transducers. Sensitivity is also improved throughnew heat dissipation technology and low attenua-tion lenses employing nanotechnology materials.

New materials, smaller subdiced elements, trans-ducer reliability, heat loss characteristics, transduc-er size and weight limitations mean making such a

T Yoshie Improving clinical performance with innovative technology

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Fig. 1: SmartFocus Cardiac 4D transducer. The smallest, lightest, highest performance 4Dtransducer to date

Fig. 2: SmartFocus Cardiac 1D

array transducer

transducer is not easy. A whole new range of ma-chining and assembly techniques had to be devel-oped in order to make the transducer a reality. Theresult is the PST-25SX, the smallest (and important-ly, shortest), lightest, highest performing 4D trans-ducer available today.

Many of the improvements that enable 4D trans-ducer can also be applied to 1D array transducers.New materials and new manufacturing techniquesmean SmartFocus 1D array transducers also featureimproved performance in smaller, more ergonomicdesigns. In particular new machining techniquesmake it possible to create elements that can vary thebeam profile over depth.

SmartFocus transducer design is an integral partof Artida’s system performance, however extractingthe most from these more sophisticated transducersrequires a new beamformer, advanced processingtechniques and substantially more computationalpower.

High-performance beamformerand processing engine

Driving a SmartFocus transducer and processingthe volume and complexity of signal data returnedis far more challenging than in a conventionalechocardiography system. It would not be possiblewithout the development of the MultiCast beam-former and the SmartCore processing engine.

The MultiCast beamformer is responsible for cre-ating an ultrasound beam that can scan 2D and 4Danatomy more quickly and more accurately. Thecomplexity of the wave pattern generated and thehigh temporal resolution at which it is created re-quire that it be fast and flexible. It contains a num-ber of innovations. It can simultaneously generatewaves patterns that focus at different depths thusallow dual focal points in an image without sacri-ficing frame rate. The MultiCast beamformer can si-multaneously transmit/receive Doppler data to/fromdifferent destinations enabling increased colorDoppler temporal resolution. In particular small re-gurgitant jets can be detected when this increase iscombined with the greater sensitivity of SmartFocustransducers.

SmartCore is the new architecture that providesthe raw data processing power required to drive thebeamformer and transducers and to provide highquality data to the display and advanced applica-tions that make this data meaningful. It combinesover 80 high-performance processors with large

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Fig. 4: Tissue Enhancement Mode enhances myocardial definition

Fig. 3: Artida

Fig. 5: 2D Wall Motion Tracking

Fig. 6: 3D Wall Motion Tracking

scale Application Specific Integrated Circuits(ASICs), Field Programmable Gate Arrays (FPGAs)and high speed Digital Signal Processors (DSPs). Thedesign objective is to provide the fastest, most flex-ible possible architecture for the processing of com-plex information. SmartCore can process massiveamounts of information and extract the clinical parameters necessary for clinical assessment anddiagnosis.

The increased perfor-mance of SmartCore al-lows numerous, previ-ously impossible imageprocessing techniquesto be applied. For exam-ple, Tissue Enhance-ment Mode offers asmoother, clearer ultra-sound image than waspreviously achievable.The noise is effectivelysuppressed, and theuniformity of the imageand the visibility of theendocardium and my-ocardium are greatlyimproved.

SmartCore is also highly configurable enablingfundamental system performance and functionalityto be upgraded in software.

Advanced clinical applicationsHigh quality data means excellent imaging per-

formance. Increasingly echocardiographers are alsoasking for advanced applications. Cardiovasculardisease is a leading cause of death and is becoming

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Fig. 7: SmartSliceplane selection

more frequent. Disease which affects wall motionand its timing can be difficult to detect with thenaked eye. Of late quantitative applications havebeen of particular interest because they offer thepromise of earlier, less subjective assessment of car-diovascular disease.

Pattern matching techniques, widely known asspeckle tracking, allow detection and quantificationof wall motion. Wall Motion Tracking can be used toassess abnormal motion often seen in ischemic heartdisease. Such abnormal wall motion can be observedeven when it is not apparent to the eye. Regional andglobal motion can be assessed and a wide range ofparameters can be observed like displacement, ve-locity, strain, strain rate, rotation, etc. These tech-niques are not subject to the directional limitationsof Doppler techniques which depend on the angle ofincidence of the ultrasound beam to the moving tis-sue. Semi-automated tracking techniques means thetotal myocardium can be quickly identified and as-sessed and a range of quantitative results andgraphical representations can be generated.

Artida features two methods of Wall MotionTracking: 2D Tracking (2DT) tracks 2 dimensionalwall motion (the projection of three-dimensionalmovement on a two-dimensional plane). 2D Track-ing can generate high temporal resolution data use-ful for techniques such as dyssynchrony evaluation.

3D Tracking (3DT) can observe total, global myo-cardial movement. 3DT is not easily achieved due tothe very large number of speckles that must be iden-tified and tracked spatially (throughout the myo-cardium) and temporally (throughout the cardiaccycle). It is not possible to achieve 3DT by simplyconducting 2DT on multiple planes. New data pro-cessing techniques including 3D speckle trackingtemplates had to be developed. SmartCore Engineprocessing power is the key in this technique. With

a full quantifiable volume available, true global as-sessment of the myocardium can be made and newparameters (like twist, torsion, etc.) can be observed.

The importance of ergonomicsand workflow optimization

Ergonomic and workflow considerations are in-creasingly important in ultrasound design. Minimiz-ing repetitive, unnatural operator movement and re-ducing the time and effort required to conduct anexam are central to Toshiba’s ultrasound design phi-losophy. Since 4D is a relatively new technology, itwas an area of particular focus in terms of er-gonomics and workflow.

There are many considerations in making an er-gonomic system. Toshiba’s ergonomics philosophy isembodied in the iStyleTM concept. It starts at the con-trol panel. Frequently used operations are arrangedaround the central palm controller so they can beactivated with minimum movement. The whole pan-el is highly configurable. Key assignments can bechanged so that frequently used functions can beadded to the panel and positioned according to theoperator’s requirement. A much greater range offunctionality is available at the Touch CommandScreen. The placement of controls of this screen isalso fully customizable. QuickScan one touch imageoptimization can also substantially reduce key us-age. The whole panel can be moved left/right, in/outand up/down and the monitor can be positioned in-dependently. A handle was added to the monitor tomake it easy to position. The system is very quiet inorder to improve both the operator and patient ex-perience.

There are many workflow and ergonomic chal-lenges in 4D ultrasound. 4D transducers are by ne-cessity larger, there are multiple steps required to as-sess the data and the practice of 4D is still changing

47

quite rapidly. As the usage of 4D increases, the im-portance of these issues will likely increase so its im-portant to pay close attention to them on a newplatform.

4D transducer design is discussed above ingreater detail but the main ergonomic considera-tions are weight, size (especially length) and foot-print. The PST-25SX transducer is the lightest andsmallest (and shortest) in class, the cable is light-weight, flexible and long so its very well suited toergonomic and workflowrequirements in clinicalusage.

Since QuickScan one touch image optimization iswell accepted in 2D echo it is a very worthwhile ad-dition to 4D. It allows rapid optimization of the im-age quality of the entire volume in one operation.

While a lot of data is available in a 4D volume,extracting the information from that volume can in-volve multiple steps. Minimizing the operations re-quired offers the possibility of substantial gains overexisting 4D solutions. SmartSlice technology wasspecifically developed to make obtaining results in4D imaging faster and easier. SmartSlice provides avariety of tools for 4D data manipulation with a fo-cus on simply and quickly achieving the desired view.For example 4D plane selection is reduced to two op-

erations by selecting an ob-server point in the first andthen a view direction andslice thickness in the sec-ond.

One difficulty with 4D incardiology applications isthe trade off between tem-poral resolution and imagequality. On Artida it is pos-sible to acquire a completecardiac volume in oneheartbeat. This method pro-vides a very consistentdataset. If users requirehigher image quality or bet-ter frame rates then its pos-sible to acquire the volumeover several heart cyclesand synthesize a completevolume. A real time displaywas chosen for this func-tion so that as each datasegment is updated the vol-ume is continually dis-played. This makes it much

easier to monitor the volume for quality before stor-ing or analyzing it. Irregularities caused by patientmovement or breathing can more easily be avoided.

ConclusionArtida features changes to nearly every aspect of

echocardiography system design. Far more impor-tant than the technical innovation though, is the de-finition of clinical requirements that these innova-tions must address. Through close consultation withthe Medical Advisory Board and users we could en-sure that the new design was targeted at real clini-cal and research requirements. Artida’s basic designphilosophy centers on advanced transducer designto provide better data, faster and more flexible sig-nal processing to extract more information morequickly, improvement to conventional clinical appli-cations and new advanced applications. At everylevel attention to workflow and ergonomics are anoverriding factor.

The final result is improved clinical performanceand a host of tools that provide new ways to assess2D and 4D ultrasound data.

*Artida and iStyle are trademarks of Toshiba Medical Systems Corporation

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T YoshieToshiba Medical

Systems Corporation,Tochigi, Japan

Fig. 8: iStyle ergonomics

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Imprint

Publisher:TOSHIBA Medical Systems Europe B.V.,Zilverstraat 1, NL-2718 RP Zoetermeer

Tel.: +31 79 368 92 22Fax: +31 79 368 94 44


Editor-in-chief: Jack Hoogendoorn

Editorial review:CT: Dr Jörg Blobel

MR: Faiza Admiraal-BehloulX-ray: Bob Eastick

Ultrasound: Dr Jörg Schlegel

Printing: VVA, Düsseldorf

Subscription Service:Tel.: +31 79 368 92 71


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+31 79 368 99 99Head Office Europe: +31 79 368 92 22

© 2008 by TOSHIBA Medical Systems EuropeAll rights reserved

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